You can also get
Belarc Advisor, run it and it will give you a detailed report on all the software you have installed on the system. It will also show the registration keys.
For example, I have Nero and when I reinstall the program I have to enter the registration key to activate the program.
If you've never done a reinstall before it can be a bit scary, but once you've done one you'll be surprised how easy it really is. That I link I gave you gives very detailed instructions, so let me know if you have any questions after you read through it.